Fix -Wunused warning with clang/gcc

- Get rid of unused argc/argv variables in main
- Bump WARNS to 6

MFC after: 3 days
Sponsored by: EMC / Isilon Storage Division

tools/regression/sockets/unix_gc/Makefile

@@ -2,6 +2,6 @@
 
 PROG=	unix_gc
 MAN=
-WARNS?=	3
+WARNS?=	6
 
 .include <bsd.prog.mk>

tools/regression/sockets/unix_gc/unix_gc.c

@@ -752,7 +752,7 @@ recursion(void)
 
 #define	RMDIR	"rm -Rf "
 int
-main(int argc, char *argv[])
+main(void)
 {
 	char cmd[sizeof(RMDIR) + PATH_MAX];
 	int serrno;